Knighted by King George the Fifth on the First World War battlefield of France, Sir John Monash was the first soldier in 200 years to receive such an honour from a British monarch.

Another century later, federal Cabinet minister Josh Frydenberg says he ranks Monash as one of his heroes.

"Sir John Monash is Australia's greatest citizen soldier - amazing feats of bravery on the battlefield and in leadership."

Before and after the war, the Australian-born Monash had a distinguished career, something his descendants are also keen to highlight.

Michael Bennett is his great-grandson.

"We'd like Monash to be remembered for his multifaceted contribution, first as an engineer, then as a great soldier, and then a nation builder later in his life."

The son of Prussian migrants, he was fluent in German, dux of Scotch College in Melbourne and completed a masters in engineering at the University of Melbourne.

He then introduced reinforced concrete to Australian railway and bridge construction.

Today, Sir John Monash is the face on Australia's $100 note.

A university and a city council in Melbourne both bear his name.

He helped initiate Anzac Day and oversaw construction of the Shrine of Remembrance in Melbourne as a lasting legacy to those who fought for the country.

As a reservist officer, Monash had risen to command Allied forces in France and delivered crushing blows against the Germans in 1918.

But he was never promoted above the rank of lieutenant-general.

Tim Fischer, a former deputy prime minister in the Howard Government, leads the campaign to, in his words, "right a wrong".

He says that "wrong" almost sidelined Monash from the final fight against the Germans.

"I think the country did the wrong thing by him, not quite as bad as the French Dreyfus affair but not far off it. And it's about time this wrong was corrected, to posthumously promote him to the rank of field marshal, as a symbolic salute. And the sooner, the better."

In the war, Australia's official war historian, Charles Bean, and journalist Keith Murdoch, the father of Rupert Murdoch, hatched a conspiracy that almost stopped Monash.

Cabinet had approved naming him commander of the Australian Corps, but then prime minister Billy Hughes suspended the decision after getting input from Murdoch.

Only a two-day visit to France to meet with Monash's fellow officers convinced him to leave the Cabinet decision intact.

Michael Bennett, Monash's great-grandson, describes the public and private campaign against him.

"They saw him as someone of German parentage. They saw him as having the wrong religion. Expressions that Bean used about Monash, like being a 'pushy Jew,' are an expression of terrible intolerance that we see in all aspects of life from time to time. I think, 'How absurd to use those sorts of concerns, personal concerns, in something as important as fighting a war and choosing the right men to lead their troops in war!'"

The officer corps stood behind Monash, finally leading Hughes to do the same.

Josh Frydenberg, Jewish himself, says he sees it as a proud moment for Jews in Australia and, now, Monash's posthumous promotion is in another prime minister's hands.

"The fact that Australia has been so welcoming to the Jewish community for so many decades can be traced, in part, to the success, the admiration and respect, of Sir John Monash. Well, I know the Prime Minister respects him greatly, and so does the Leader of the Opposition Bill Shorten, and, obviously, Tim Fischer, who's been a proponent of this initiative and spoken to many of them. So I am very confident there will be strong bipartisan, and cross-party, support for this initiative."

Supporters say they hope Monash will be promoted to field marshal for the 100th anniversary of the end of the First World War next year.

He would become only the second Australian-born person to receive the rank.